turn now to an alarming new consequence of this year's extreme her. A deadly outbreak of the west nile virus. Mosquitos are affecting everybody across the country they're so bad in texas they're planning to attack by the air. Abc's ryan owens reports tonight. Reporter: Crews in gas masks and chem suits stray around dallas schools at night. Trying to make sure mosquitos are gone by the time students return to class later this month. Dallas county home to almost 3 million people just declared that public health in which. It's never seen this many cases this early in august. They've been spraying from trucks nearly every night but it's not enough. So the county has now approved dumping pesticides from the air over these heavily populated areas. We're talking about a third world virus that we don't have a blue prints to say this works versus, you know, another plan. Reporter: Scientists say the virus is more common because the unusually warm winter meant fewer freezes that killed mosquitos. West nile has been reported now in 42 states. 241 people have been diagnosed. Texas has been hardest hit. Dallas county alone has seen more than 175 infections with nine deaths. This 39-year-old dallas area landscaper was bitten a few weeks ago. Yeah, definitely sicker than I've ever been. Reporter: Late august and september are peak times so crews here will keep spraying hoping to slow a virus that's killing more often and earlier than ever before. Ryan owens, abc news, dallas.

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